Party-line telephone system.



E EATENTEE MAY 21, 1907. G. E. TERHUNE, w. M. BIDSON a; w. B. HUSION.

PARTY LINE TELEPHONE SYSTEM.

7 APPLIG A'I'IOH FILED NOV. 11. 1905.

4 SHEETS-SWEET 1-:

ATTORNE PATENTED MAY 21 G.E. TERHUNE, W. M. EIDSON 6; W. B. HUSTON,

PARTY LINE TELEPHONE SYSTEM.

APPLICATION FILED HOV-11. 1905.

4 SHEETSSHBET 3 kmmmmw ATTOHNE r? N0. M45543. Pi-JQPENTED MAY 21 190?. Q: E, TBRHEWE, W. M, EIUSWF 1 W HUSTGN.

PARTY LINE TELEPHONE Ammonium FILED 210 1.11. mm.

. n A f/WTNESSES: la

Indicatecorresponding v NI n strA'r as PATENT oFrIoE.

GUY a. TERHUNE, WILLI'AM ,EmsoN, AND WILLIAM B. nos'ron, OF

' WILLOW HILL; ILLINOIS.

PARTY-LINE TELEPHONE SYSTEM.

To all whom it may concei'n:

Be it known that we, GUY E. TERHUNE, WILLIAM MI EIDSON, and WILLI'AM B. Hus- TQN, citizens of the United States, and residents of Willow Hill, in the county of Jasper and State of Illinois, have invented a new and Improved Party-Line Telephone sys tem, of which the following 'is a'full, clear, and exact description.

more particularly. to as'ystm for accomplis'hingthe followingp'urposes, to wit: 1. To provide anreflicient and simple lockout for preventing eavesdropping and interruption in conversation; 2. o conceal the identity of such stations as maybe busy,- thereby prevent-ing operators at other stations from ascertaining or inferring what persons are talking 3. To bring all business of the line under direct surveillance of the o era tor at the central station, thereby faciitatrhg the,ascertainment of tolls; 4. To provide a selective callwhich disturbsno statioiijzexcept those desired; 5. To provide certain; constructional details looking toward simplicity, positiveness of action, and generlihelliciencyof' the party line.

Reference is to be had to the accompany-c ing drawings forminga part of thisspecificatron, in which similar characters of reference Figure 1.is a diagram of the wiring connecting together the several .-subser1bers statiors and the central stat1on,;- ;F1g.:2 1s adiagram of the wiring, pecul arftto a subseriL-ers 'sta'tionand s liownngjfthbgconncctions of this wiring with the central stat 1on-A;:'

Fig. 3 is a elevation of the, contact mechanism used at each subscribers,stat1on,;and of the means for actuat t the same step by step; Fig. 4 is a'vertioal section-upon the line 4-4 of Fig 3, looking in the direct-ion. of

the arrows, and showing the details of the" contact mechamsm and of the step-bystep: the same Fig. 5 1s a movement for actuating fragmentary elevation, partly in section, of the switch hook, the contact mechanism therefor, and the lookout for preventing the switch hook from rising; Fig. 6 is a front elevation of the magnetically operated lockout mechanism; Fig. 7 is a fragmentary detail, showing'the normal and abnormal contacts operated by movements of the switch hook;

Fig, 8 is a fragmentary elevation of the Specification of Letters Patent. Apnlieatiou filed liovointor 11, 1905. Serial No.'286,865.

crank 25. Mounted ri parts in all the figures:

this-shaft 27 is a gear.

Patented May 21, 1907.

calling mechanism used by the central station, this' calling mechanism including an tails whereby system; and 1 section throu h the induction coil.-

The severe telephones numbered 1 a 7 severalsubscribers"stations, are shown in the upper portion of Fig. 1. These tele phones are connected in series with each other and in the lower line wires 13.

ith the central station A shown 'lhe last station of the series is connected with the ground by means of a a ground-wireigl. At the central station A is located a c op'lfi, grounded at 18, 'a jack and an operators tele upon a board 22 a main battery 17 19, a jack hone 21. (see Figs. 8 and 9) is a frame 23, and journaled within the frame and board is a rcvoluble shaft 24 provided with a hand lug is a pinion 26. Anot 161' revoluble shaft 27 is provided with a needle 28 which moves around overa dial 29 30respectivelyrepresenting the several sub-' provided with ordinals scribers "stations. Mounted rigidly upon the pinion'26. A toothedwheel 32 is also mountedrigidly upon the shaft 27 and is engaged by a spring-pressed pawl 33 as will be understood ported upon a pin 34. [A contact lever 35 is journaled at 34" and is provided with a detent 36 which is caused tofoscillate when the toothed wheel 32 is rotated as will be understood from Fig. 8. A spring contact ton e 37 is mounted upon the outer or free enfdf the lever 35. A spiral s ring 38 tensions the contact lever 35, norma ly maintaining it in its lowermost osition. .Contact screws 39, 40 are respectlvely disposed above and below the contact tongue 37 and are mounted upon metallic ln s 41, 42. When the crank 25 is rotated by land the spring tongue 37 is caused to engage and disenga e the contact screws 39, 40 as indicated by otted and full lines in Fig. 8.

part of t'hisfi'gure by means of h ounted idly upon the shaft 24.

31 which meshes with indicating dial; Fig. 9 is ahorizonta'l sectionppon the line 99 of Fig. 8, looking the;

direction of the arrow and showing the de- I successive electrical impulses into the line; Fig. 10 is an elevati0n,.partly' In section, or the induction COll used in our Our invention relates to-telephony, and 1g. '11 is a vertical transverse 10, 11 and 12, located at the from Figj 8, this pawl being sup- Thelug 41 is connected by a. l

. wire 43- with the met. batt'e 42 connected by a Wire 44 with theicontact Q 2 "filingsandthe lug" spring 45 of the jack 1'9. The'contact plate 146 ofthis jack is connected by a Wire 47 with.

the drop 16, a wire;48 connects therhaih battery 17 with the ground 1,8,awire 49 c0n-' nects'the sleeve 51 of the jack i9 withthe ground wire. 48, and a wire connects" the wire 4Q With' the drop 16. The plug 20 is provided 'with a tip 52 and with a cylindrical contact 53. This plug is connecte by wires 54, 55 with the operators, telephone 21.. The

' receivers are shown at 56 and are mounted respectively upon switch hooks. 57'." A bracket 59 immediately. aboveeach switch contact members togetherfconstituting ftivo i abnormal contacts which n g closed when the receiver 56 is removed from'jthe-hook. Each switch hook isprovided with aspring whereby it is retracted; and is'al'so provided with a pressure 'r'oilen'fifi ofinsulat'ing material. for increasing and; decreasing the distance between {the springicontact rnem' bers' 60 and 63, as will buriderstood; from Figs. 5 and 7. "A magnet "67. isflprqvided with an armature-68,?jthe latter Ibeing -re-' tracted bymeans of a spring 68 .and nor mally occupying the position indicated in Fig. 6. The-armature-G S, is mounted upon the lockout lever. .69, 4 the latter being journaled upon a bracket Z0 and adapted .to swing sh htly. I The bracket-Z0 "is 'rnoiinted hoard 71'. n-T hejloekout lever 69, w en in its normal position engages a stop pin 69, and while in this;positron-prevents the switch hook 574mm rising. A, contact screw 72 is threaded-through a-bracket573 and disposed adjacent; tothe n agnet 67. order to enable thelockout; lever fiQjto be more effective in holdingidowln the switch hook 57 it is provkledwith aniotch Z4-as indicated In, F 1g. 62 "The subscriherfsbell'is;

. shown at 75and a local baaerym 76."" ;The-.

purpose of-Lthe notch 74 is to gcatchithe switchhook 57 and prevcnty t he sainifroinrising should the rcceiverbcremoved bya subscriber whilethe 'n ecl'i'anismisworkm That is if a subscribershould seek to cafe 1; in as his unlocking positionis passed over) The three windings 77," 78jaiid 79 are mounted upon a core 7 7, and .togcther constitute an induction coil, ,tiie'de tail's ofiwhich; are shown more particularly in ,Fig sblfl. and 11. The transmitter is shown at 80 and .the' transmitter battery at 8!. 1 Themagneto generator isshown at 82 and maybe, rovided with a handle 82" and otherwise 0 Jondinary construction. At 83 is shown a magnet-provided with an armature 84, the latter being mounted. upon anv arm 85 which is jourbe seen by o.omparin tho .rclatiyepositions' nah-d a1 86 and is tonsionvd by mcans of a. i

spring 87, indicating needIeSSaisc n- 'nected .with thearrn 85 and is adapted to swing'when themagnet 83 is energize-d. Be-

85'andthe i eedle 88 normal sitioniidi cated in. Fig. '21"-Theneedle' 88 H swung to ;,the -left according to the View shown iii-Fig. 2-, indicates tothc subscribe-rat that station that the line is open forbusincss',

but. when s lv'l l ii in the. opposite'zdirehtion, or

to, the'rightof; the, positionindicated in Eig.

2, the needleindicateslthat.the'.line is,busy.'.. l

Appropriatelcgendsf open and bus'y are, therefore,employednaseindicated in Fig.

2, forap rising tlleLsuhscriber of-,the=condi-, j

when in its normal position, that is, when tion of;.t e line; *tflhestcp hy step contact 1 mechanism located .ateach subscri bersstationisfishown in Fig. .3. magnet-891's mounted upon a-bas'e 90; and uplon this base f are twonverticalplatesm .92. ,zAi-brackct 93 islikewise niountedupon-thebase-90. Jour I Q naled .within- :this; 1bracket-Iand, ,su pp'orted thereby is a lever94,-supportednpon a trunnion:94, providedwith firspli llgigiwhicli811-.

gages an adjustableiscrew 96 by means of wllichwthetensio'n of .thespring ma be regu- .ver'94terminates-in a head 98 provided with "bevels: 99 100. 7 A revolxibleshaftlOl is journaled upon-the verticalsplates gland 92' A -.tooth'ed.wheel 1.02 is rigidly: niountedfupon Qthi'sfrevoluble shaft and'isso located as to'be engagedalternately by the bevels 99 and 100. in-such manner-as to rotate step by. step :when the lever 94 movesup irnddown wi thin a vertical plane. A contact wheel 103 is 103" disposed equidistant. The.' number of.

- be. seen: by. referring; tottl e aippezportio n pig-Fig. ;1,- tl ie .several.contact-wheels I-103,. at thc' di-fi'erent subscribers stationsare Po itioned -,relatively .to .each other that :tl ehlanksnaces 1 l 3' -.arc disposed Iatdiflcrent angl'csf .Eor,convenience,';tliesc .SINWPS may he lat-ranged .as. .shown, .each successive stationhavnig iiscontact'wheel. 103 so-pos'i- ;ti ine'd ,that 'theseveral spaces. ordg'iauks 103" "of one,subscribersstation;is on c- -two|fth-of.a revolution :r mqvml .from that- .of thei nex't q dated atfwill. 'Mountedju'pon 'the ever 94 is an armature 97in:- themagnet 89. The le- TOO 'provided'witha number of contact points succeeding subscribers station. This may the stations numbered ,1 2, 3 4, .-5 6, 7, 8, 9,

r at one subsqribers station the contactpoint 5.

' contact point is moved angularl a little to the transmitter'80 is connected b'y'a wire 11 1 withthe magnet S91 J .wire 115 leads-to the generator 82.10011- a contact spring and: above the contact nected by a wire 129 with the gle contact points 104* at the respective stas tions are displaced to some extent as between two consecutive stations,the idea being that,

104" may be directed downward-whereas at the next succeedingsubscribers station the right, and at the nextsubscribers station the eneratorof the calling subscriber throws the; mp 16 and attracts the attention of the operator at the central station, the two succeeding impulses merely causing the drop 16 to to click twice, or serving in any other appropriate manner to inform the central operator as tothe total number of impulses. The generator circuit is as follows':-ground singlecontact point is moved still farther-to- -1'8 at the central station, wires 49, 50,.dro

the right, and so on throughout the series.

16, wire 47, contact members 46, A5 of jac Mounted above the contact wheel "103 is a "51, wine 44, contact members 40, 37, arm 35,

wheel 104 is another'contact spring 106, these springs being supported upon posts 107, 108 which are provided, respective'l with binding posts-109. 110 (see Fig.3). T s

with the winding 77, and bya wire 112 with. the battery 81. by a Wire 113 wit the contact spr ng fih some and line 13 to subscribers stations in series. The circuit through each subscribers sta-r tion is as follows: Winding 78, wire 1 14, magnet 89, wire 115, generator 82, wire 117 to line 13, and ultimately through ground wire 14' to ground 15. tral station being thusiapprised that sub-. his battery is connected 'seriber N o. ,3 desires to communicate with The operator at the cenperson inserts the plug 20 into the jack e winding 78 is connected by a Wife 114 :19, thereby throwing intocircuit the operavFrom the magnet 89a one 21, and removing the receiver nected with the wire 1l5'is'a wire 116 which bring the needle 28 over No. 3, designating leads up to the rocking arm 85. From the generator 82 a 'w re'117 leadsto acontact In doing this, the rota- 118. Connected with-the magnet 83 is a the toothed wheel'32 to raise and lower the wire 119 and. a battery 120. Through a wire contact lever 35 several times, thereby send- 121 the battery is in communication .with the shaft 101', and consequently with the contact wheels 103 104. s ring 106 is connected by a wire 122 with t ing the number of successive im' 'lulse's over the line, The circuit of these impulses is as The contact followsz-grouxid 18, .wire 48, main battery 17 wire143, contact members 39, 37, contact e magnet 67. The contact spring l05 is. .lever 35, line wire 13, and thence in series connected by a. wire 123 with thennagnet 83, I through the several subscribers stations, the

. w re 128 with 'l 79. The-receiver is also connec of a wire 130 with thecon'tact'spring 62. The lug-"i3 holding thecontact fscrew, 72 is connectedlby a wire l31j-with the contact spring 64. -7i'- tg;--'l -fjf m The operation of our system is asf OWS munieate with subscriber N058, gHeisunv andat-the-sa by means ofrotation of this w circuitoontinuing' as follows: winding, '78, \vire,,114,.'magnet 89 wire 115, generator 82, ,wire'117, line wire 13, and thence ultimately to ground 15. Each impulse thus sent over the line by .the,eentral operator energizes S the ma net89-at each subscribers station, ndin 79by and eath 1m v n the rocking ever 94 downward and then al- The reiver is consultis that the bevel edges 99, 100 turn the toothed wheel 102 ste by -step, the amount r heel corresponding to that of..the wheel 32 a t=the central station. At the instant when the needle 28 at the central station rests upon the, ordinal 3, the revoluble shaft] 01 at station No. 3 is in slIdl1po-- I r sltion that'thecontact wheel 103 presents-the Suppose that subscriberNogii desires to cone, 4 blank or spaculse causes this magnet to pull 0w it toresumeits normal. position.

e 103. to the ci'intact spring 105, istantjthc co'ntact'wheel able to do this directly,'- fo r the reason that 104 presents-the iiontaetzto'oth 10491.0 the 15 free, however, and by grasping the handle- 52 and actuating the generator a number of tunes corresponding to the number of lllS stastation at a time.

contact sprihglOG; It is evident that this relative arrangement of the contact wheels I 103, 104, and the c ntact springs 105, 106 His generator"82 cannot occur at more than one subseribers In other words; when the contact tooth 104 engages the spring 106 and the contact spring 105 rests within the tion, he is able to apprise the central operator, blank space 103 at station No. 3, it is clear as to the number of the calling station. ,In' the instance under consideration he. rings that at no other subscriber's station can the contact tooth 104 engage the contact spring three times. The first impulse made by the 106, nor can the contact spriug'105 be out of WM n"... V

electrics i1 conimunicati'on'with the contectJ stationNoi '3 the '83 is' unzii le-. t-o,

wheel 103. .Hence, the condition of tlielocal;

circuits controlledhy thecontaclt heels 103,

104 is different atthe subscriber 8 station just answered by the central;'opmtorthaniatthe other subscribers" stgi'cionsi; a

Thelast-impulse pose the central stationja'nd leaving 'the contact" wheels -103 eni-104 .at station N o. 13 yin'ithe' eondition above described; completes a 1micircuit at st'a-tio'n 0.. '3 as follows battery 120,wire- 121; shaft; 101 contact wheell'fli;

i contrasting Figs. 5' m l(l '.7 'lll' tolliiii' gb cult between the sjuhserihorzrt station" mutoly through grouri'fl U I The winding-78, acting induct vely iiponjthei.

-movement of the comes-M51 69 4mins ft h' contaet' screw"? 2 (see'dottedl'inesi'hFig' completes a-nothefllooa'i z' ireyity: as? follows: battery 76 Wire 124-; braleke't 70,-}iloelt'dut 7.5, in-r8125 lmokto 'bi ttry ro. This-rin e continuous alariu'gzi've As abovezdescrihilfthcli'iokoiitfei'iii fi no longer within tliopatlij olf th sw'r 57, and the switch-hookthoroforifrisei abnormal conflicts as will h'o'unglerjstibod hy' 11'5" tip 52, cont-ooh nclnherlfi-flwire V members 40 and -37'," lover 35', line suhscriliors station "NO.""'3,- 'Win(lii k H4, im gnot'sil, wire 1'1 5, generator, 2; wi

winding 79, induces talking 'curr'entsithrouglr the following oirouit. Receiver 56", Wire 1301 contact spring 62 (see-Fig fin' mntaictispr'ing 63, wire 127; ire 126; win'ding'.-79;.wirol29 1 A I lends 1o retain-ii to its finorr'imlpositionjbut'as book to receiver 56.

The cii'euit't'lii ough tho receiver 56 is therefore lot-e11 I circuit is .theroforo -ulso 'loci i'li ""x\ t istotio No. 3 the circuit throughmhglii ifiliiifiszioces sarily open, owing totlie factrtliofiatlhisstiition only, the sprin lii rigoverthe line from to open .the normal'i-ontaotioniltb olo's'etlie fvrith'some other si'ih's criherisoy at station N0, r00

"Hra Etheerm 85, and as aconsequehc'e the in dic'atingneedle 88 occupies the. osition indicated int-he upper portion of ig. '2.-rest ing" o heiflsiibsori' ers jstut-ion's however, the 'con iglition 0f the contact-wheels 103, "1 04 is suchthatfth'e condition of thev circuits controlled 2 these:-contaet'wheelsis reversed as com-- 1 -pe.redfiyith the condition of those circuits at statioii Np. 3. That is tosny, a'tfell stations except? steltidn; No. f3 the local circuitjcon-wetrolled l-by cont-pct spring 106 isnow 0 m,; ,yvlier'zis theilocal circuitjcontrolled bv the necess iribiso; for the reason that atoll star-l tionsfJexcepflNo'; 3 theflcontncts'pring 1057 rests upon someone-oi the contaeti oints 103: (See-lop or ort-ion of Fig i. ,At

.wire "121,- shaft" lonw mm wheel 103, con- {tactspring- 105, Wire 123, magnet 83, wire '119, imcloto hatter}; 120. ThlS energizes 'fihrdW-tlie indicet ingnetlle"88 to the right =accordingft -the'vie vshown inFig'." 2, so thfitfl'h i1CdlLSS will restupon the'legcnd jfBnsy-ff *Hence; at each subsorihers star-ff 'tiqnfexce ts tation' No.3, the busv signal 5- is displeyed' forthe time being} w iereas at. 't'heYsta'tion"'No.;:3 the indication is gire nasl' open? Subscriber N o. 3 now tells the eer e irnlfiperii wfithat'he desires to communicate- 8. }Thfopei it0r1 at the central station "threilponrot'atelsl the crank 25 until the noes fdle restsu ,'n;the number of the sietioinl desire lfl In" t 9 present. instance, the neeille V frests'fupon'i theordjnall 8. (See position-of 10 the needle 28in full-lines, Fig. 1.) In doing this,ftheoper it'or 'at the control station'now, I

seii'ds' a'nu mberj'of impulses over the one, one 1 erg'izin{1,1v endldenorgizingfthe several magi nets 89 i t. -:the'respec,t1ve stations as above FdGSC-libfidff 1 In doingiil igjthe, contact wheels 103,104 at all of the su'i-jscrihers stations re 1 ;ti 1rne l','! m(l consequently at station N o 3'tl1e eonmer i s brokeii between the 'contaot spring t he, subs riber ilreedlif romoved' hisv "re- ;i1.s-':1Tppermestp ition; the tendency of r the y d lTIIi' GQItoi-rei iim to it's norm il o si- "tion'itioe ofi disturhthe connection o *the suiiscrih t this' stallion?! 5 T 'As tlie'ooritiicti'wlieel '103cm!'l04 iii cur-h 2 'istnt io'irt-urii step hjgitp 't-he' se brixlr lookout for ill, thosuhs'orihors stations oresur- 'cossn'oly* inm orl' towiril the magnets 67-, 'Whig ?"iiioi'e noni'.is only moniontury mull Contact sprii g' 1O5 is now closed. This" is 86 v 'eecii st'ationjot er t :m- NQ. 'tlie circuit'is g now completed as'lfollows:-betier3" 120,-

1106 amt-she can nes-moth 1045180; that the j; 1 i

thelockout rid-169, The'fletter thereupon co iver56 lnild' conseqliently his hook 57 isiri .izo

iloos iiut'aill'm'd Him. for anysubscriber to ro- 0 r ing energized, leaves the arm 85 and the indi- 2 5 magnet 67 the switch hook 57 of that station move'his receiver. The result'is thatto all intents and purposes the receiver'hooks at all of the stations continue locked. The requisite number of impulses having 'beengiven ,5 as above described, the contact wheels 103 and 104 at station N 8 are brought into the position indicated ,in Fig. '1. The. contact wheel 10 4 being new in communication with the contact 3 ring 106, and communication is being broken tween the contact spring 105' and the contact wheel 103 at the stationcalled, the result is that] the magnet. 83 at that station being under the control of the contact spring .105, ,and cons'equentlynot beeating needle 88 in the position indicated in Figs. 1 and 2. "In this position the needle 88 indicates open. At the othersubscribers stations, inc uding station No.3, the needle 88 indicates busy as above described. At station No. 8 the engagement of the contact tooth 104 with the contact spring 106 energizes the l-nagnet 67-as above described with reference to station No. 3. -In energizing the is unlocked; so that the operator may remove the receiver 56. The engagement of the lockout arm 69 at the called stat1on (No. 8) with the contact screw 72, completes the cir- 0 cuit of the battery 76 through .the bell 75 as; above explained, thereby ringing this bell continuously so long as the receiver 56 at that station remains on the hook. When, hone ever, the receiver in question is removed, the action of the bell is stopped by disengaging the normal contact members 63 and 64, thus openin the bell circuit. Conversation may now ta e place between the subscriber at station No. 3 and the subscriber at station The conversation being finished the subscriber at station 10. 3 'merely' hangs up his receiver, thus restoringthe normal connection. The subscriber at station No. 8 now grasps the handle 82 of his generator 5 82, as indicated in Fig. 1, and rings off. If he fails-to do this and ban s up his receiver. 56, he merely closes the bcl circuit which, it will be remembered, he opened by removing his receiver. ll, therefore, he merely hangs 50 up his receiver and starts to leave the telephone, his bell reminds him that he has failed- I tween the tooth'lO ifa'nd the contact spring 106 atstation No. 8. 4

l It will be noted that whenever two sub scribers stations are connected for conversa- {v tion so thatthe busy? signal isdisplayed all. along the line except at one station, the arm 85 at each station except one engages the contact'screw 118. "This isa neee'ssa incident to.the display of the busy si'" a .(See'Figs. 1 and 2.) The engagement 0 the arm 85 with the contact screw 118 closes the line in frontof the generator and thereby incapacitates the generator from'afi'ecting the linewhen the line is busy. Hence, when two canso actuate his generator as to cause annoyance. the subscribers station at which the busy? w re 116, arm 85, contact'screw 118 to line ence being that instead of the current passing from the Wire 1 15 through the generator 82 to the wire 107 it passes from "the wire 115 to the wire 116, and thence through the con tact arm 85 to the line 13. The release of the line afterthe ring oil by the subscriber at station No. 8 leaves all of the magnets 83 denergizeil so that at each station the indication Open is displayed. The several magnets 67 are also left denergized, and therefore the lockout arms 69 are in such po sition as to prevent removal of any receiver upon the line. The system-is now in condition for another subscriber to call.

It will be noted from the above descri tion, therefore, that no subscriber can cal any other subscriber upon the same line Without apprising the central operator in'order that the tolls may be properly charged. Also that .the central operato is necessarily informed as to any overtimp use of the line in order that a charge may be made as compensation-for this overtime. Eavhsdrop ing is completely prevented, for-the reason t lat no tmns are engaged in conversation. Attention is called to the construction and action-of the mductlon coll shown more parto ring off. In order to ringoll' he merely sends an impulse from his generator"82 over the line, and this actuatcs themlrop 16 or 5 5 other appropriate mechanism at the central station. The central o mrator in order to ring ofl' merely turns the handle 25a distance suliicicnt to remove the indicating needle 28 from the ordinal 8 upon which it rests to a co point intermediate of any two successive or d inals. A comparativcly small degree of rotation will sullicc for this purpose. All that ticularly in Figs. wand 11. In this the mid"- dlc. winding 78 is secondary to the primary winding 77 but is primary to the outer winding 79. By using this coil the articulation is rendered much more distinct, and both the transmitter circuit and the receiver circuil'. are rendered local.

The main purpose in building, the induc tion coil and in connecting the wires as shown is to both diminish and cqunlizclllc rcsistaucc otherwise offered by. the l-'l ('(iV('IH.

is necessary is to turn the toothed wheel 32 a snlli icnl distance to break cngugcmcnt bo-,l

That is to say, if scvcral receivers drie -connocicd upon the mam hnc 111 the usual man That is to say, the circuit through subscribers are conversing no other subscriber signal is displayed, is as follows:line 13, w nd1ng78, wire 114, magnet 89, Wire 115,

13. This circuit is practicall r the same as the circuit'above described, t e only di[ fer-' subscriber caneven ascertain what two sta 

